Constant-velocity joints have been used to transmit torque of a vehicle drive shaft to an axle.
Since constant-velocity joints allow angular displacement between the driving shaft and the driven shaft with the two shafts rotating at constant speeds, they are being used not only in motor vehicles but also in various industrial machines, home appliances, office machines, etc.
There are two types of constant-velocity joints, namely, fixed constant-velocity joints, which only permit angular displacement, and sliding constant-velocity joints, which permit both angular and axial displacements. JP Patent Publication 2007-255511A discloses a sliding constant-velocity joint.
The constant-velocity joint disclosed in JP Patent Publication 2007-255511A is what is known as a tripod type constant-velocity joint, and includes an outer ring formed on the inner periphery thereof with three axially extending track grooves so as to be circumferentially spaced apart by 120 degrees from each other, and a tripod member mounted inside the outer and formed with three radial protrusions (trunnions) slidably inserted in the respective track groove, whereby torque is transmitted between the outer ring and the tripod member.
The outer ring has bulges between respective adjacent pairs of track grooves. Each of the bulges is formed at its distal end with a pair of tapered surfaces inclined in opposite directions to each other and defining an apex at the center of the bulge with respect to its width direction. Each protrusion is formed at its front portion with a pair of tapered surfaces inclined from the widthwise center toward both sides, of the protrusion, thereby defining an apex at the widthwise center of the protrusion, whereby the tripod member can be easily fitted in and removed from the outer ring.
The tripod type constant-velocity joint disclosed in JP Patent Publication 2007-255511A is advantageous in that the tripod member can be easily fitted in and removed from the outer ring, no grease lubrication is necessary, and it is lightweight and small in size, and produces less noise.
The constant-velocity joint disclosed in JP Patent Publication 2007-255511A allows the axis of the driving shaft and the axis of the driven shaft to be inclined relative to each other with a relatively large angle therebetween, provided the two axes intersect each other in or near the joint.
However, this constant-velocity joint does not allow the above two axes to be inclined relative to each other with a relatively large angle, if the above two axes intersect each other at a position remote from the joint. Also, this constant-velocity joint does not allow too large an offset between the above two axes if the axes are parallel to each other.